Conventionally, there has been known a lighting circuit for a light emitting element such as an organic EL element or the like, which is configured to generate a PWM dimming signal having a duty ratio corresponding to a light emission level specified by a dimming signal, and perform the dimming control.
For example, Japanese Patent Application Publication No. 2009-54425 describes a lighting circuit configured to perform a so-called burst dimming to stop the light emission of the light emitting element during the OFF period of the PWM dimming signal.
For example, in case of using an organic EL element as the light emitting element, it is problematic that audible sound (noise) is generated from the light emitting element when the frequency of a signal for performing the burst dimming is about 1 kHz. The organic EL element has a larger light emitting area compared to, e.g., a light emitting diode (LED), and thus the audible sound tends to increase.
Generally, the audible frequency range is from 20 Hz to 20 kHz. Thus, it is conceivable to operate the light emitting element by using a signal of a frequency exceeding the audible frequency range, e.g., a frequency of 20 kHz or more. However, it is difficult and expensive to stably operate the circuit which generates such inaudible high frequency signal.